Stabilization of tetraethyl lead



Patented Nov. lO, 1942 2,301,370 STABILIZATION or TETHYL LEAD a corporation of Maine No Drawing. Application February 26, 1941, 'Serial No. 380,604

gcl. 44-49) 8 Claims.

This invention relates to the stabilization of tetraethyl lead and particularly to the stabilization of tetraethyl lead in motor fuels.

It is common practice to add to motor fuels a composition generally known as ethyl fluid consisting principally of tetraethyl lead and small amounts of ethylene dibromide, ethylene dichloride and other substances, in order to increase the anti-knock value of the motor fuel.

of gasolinepumps which become fouled and require frequent cleaning. Loss of the lead compound through precipitation also tends to lower the anti-knock value of the motor fuel.

We have found that the addition of a very small amount of a surface-active acid ester of polyphosphoric acids or salts thereof to motor fuels containing tetraethyl lead will stabilize the tetraethyl lead and prevent cloud formation and deposition of deteriorated or partially decomposed tetraethyl lead. The compounds of this group of tetraethyl lead stabilizers are anionically surface-active, that is, they ionize in the presence of water in such a way that the cationic portion of the ,molecule is relatively weakvand inefiective as compared with the aniomic portion of the molecule which is comparatively large, negatively charged and capable of exerting a considerable surface-active efiect. The ionization of the surface-active acid esters of polyphosphoric acids of our invention may be illustrated by the dioctyl ester of pyrophosphoric acid as follows:

0.11M o- In addition to the acid-esters of polyphosphoric acids we find that the metal, ammonia, amine 'and amidine salts thereof which ionize in water to form weak cation-active radicals and strong anion-active radicals also are very efiective stabilizers of tetraethyl lead in gasoline. We do not'claim the amidine salts of acid esters of polyphosphoric acid as new compounds since they are the subject matter of an application Serial No. 390,536, filed April 26, 1941, by Walter P. Ericks and James H. =Williams.

Another important characteristic of our stabilizers is that they contain in the anionic portion of the molecule one or more non-polar groups having an aflinity for mineral oils, which groups for lack of better terminology may be called lipophile groups. These groups in the molecule tend to solubilize the compound in gasoline and for greatest solubility should be alkyl chains of 4 or more carbon atoms. We do not wish to exclude alkyl groups of less than 4 carbon atoms or acid aryl esters from the scope of our invention, however, since these compounds and their salts may be dispersed in motor fuels and have a stabilizing effect on tetraethyl lead contained therein. Although we do not intend to be bound by any proposed explanation of the mechanism of the stabilizing action of our compounds their effectiveness appears to be due to surface phenomena brought about by the action of the anion-active portion of the molecule which is probably attracted to and peptizes the extremely small particles of deteriorated or partially decomposed tetraethyl lead, thus preventing their growth and precipitation from the motor fuel. Accordingly, any acid ester of a polyphosphoric acid or its salt which is anionically surface-active will be found to stabilize tetraethyl lead in gasoline in accordance with our invention.

The stabilizers of our invention are ordinarily employed as the acid esters of a polyphosphoric acid since these acid esters are soluble in gasoline to a satisfactory degree. We may, however, use salts of the acid esters such as those of the metals sodium, potassium, lead, etc., or the ammonium, amine or amidine salts. As indicated above the acid ester should be of an aliphatic alcohol having 4 or more carbon atoms such as amyl, octyl, or lauryl on account of the greater gasoline solubility of these acid esters. However, aryl acid esters as 2,4-diamylphenyl pyrobefore it is added to the gasoline. characterize as oil dispersible both those comphosphoric acid or di-octylphenyl pyrophosphoric acid may also be solubilized in gasoline and employed.

' As considerable confusion and uncertainty exphosphoric acid or. salt thereof we mean to include the mono-, di-, triand other possible esters or mixtures thereof having one or more acid groups either in the free state or combined with a salt-forming radical. Conversely, when we refer to a specific acid ester such as dioctyl acid pyrophosphate we wish it to be understood that this term covers the commercial product known as such but which pmbably contains minor amounts of other esters. Mixed ester acids are also meant to be included within the purview of our invention.

The amount, of stabilizer used depends, of course, on the amount of tetraethyl lead in the gasoline. We have found that ordinarily 1-10% by weight of our stabilizers based on the weight of tetraethyl lead in the gasoline is suiilcient for most practical purposes. The amount of tetraethyllead in gasoline varies considerably and may run from 0.01 to 0.25% of tetraethyl lead based on the weight'of'the gasoline. The amount of stabilizer which we use'will therefore vary to about 0.0001 to 0.025% based on the total weight of the gasoline. With ordinary commercial gasolines, we have found that0005% (50 parts per million) by weight of our stabilizers will stabilize the tetraethyl lead sati lactorfly.

Our stabilizers may be added to the gasoline directly or. preferably, dissolved in a suitable solvent such as naphtha, alcohol or benzene and then added to the gasoline in desired proportions. Some of the individual compounds of our group such as for example sodium dioctyl pyrophosphate are diflicultly soluble in gasoline directly but may be dispersed in effective amounts by means of a mutual solvent such as sodium naphthenate or petroleum sulfonate in whichthe sodium dioctyl pyrophosphate is first dissolved We therefore pounds which are gasoline soluble and those which can be dispersed therein by the use of a mutual solvent.

Our stabilizers may also be added to motor fuels containing adjuncts such as benzene or alcohol'for thepurpose of stabilizing tetraethyl lead contained therein. They may also be added directly to the ethyl fluid with additional amounts of solvent, if desired, and sold and shipped in this form. In this way the addition of tetraethyl lead to the gasoline and addition of stabilizer occur simultaneously, thus avoiding any chance of decomposition after the addition of ethyl fluid.

In order to illustrate the effectiveness of our stabilizers a number of them were tested on 9. directly comparative basis. In these tests a commercial sample of gasoline containing ethyl fluid was placed in a 4-oz. screw cap glass bottle and noted. The results are given in the following table:

Time in hours for cloudtoappear Gasoline A:

' Control 1.8 v

Octyl pyrophosphoric acid 12.3 Octyl tetrapolyphosphoric acid 10.0 Triamyl amine octyl pyrophosphate 7.8 Dibutyl amine octyl pyrophosphate 10.0

. Moncamyl amine octyl pyrophosphate 5.0

Gasoline B:

Control Octyl pyrophosphoric acid 8.0 Octyl tetrapolyphosphoric acid "1.0 Dibutyl amine octyllpyrophosphatenn. 11.0 Sodium octyl pyrophosphate-sodium naphthenate 9.5 Sodium octyl tetrapolyphosphate-petroleum sodium sulfonate 12.0

Gasoline C:

Control 1.5 'n-Butyl guanidine octyl pyrophosphate 6.0 Eth'ylol guanidine octyl pyrophosphate 6.0 Diamyl guanidine octyl pyrophosphate 6.0 Diamyl pyrophosphoric acid 4.5

General Electric S-l type. The time required for the appearance of an observable cloud formation was noted. Samples of the same gasoline but containing 0.005% of our tetraethyl lead cloud formation inhibitor were also exposed to the strong light in the same manner as the control sample and the time for cloud formation Tests werealso made on the gasoline to determine what effect the addition of our stabilizers might have on other gasoline characteristics. In the copper dish gum formation test it was found that in the presence of our stabilizer gum formation was reduced almost 30%. In the presence of monobutyl para amino phenol, a wellknown gum inhibitor, it was found that the oxidation induction period as measured by the A. S. T. M. oxygen bomb test wasincreased by the addition of 0.005% of our tetraethyl lead in which R. is an alkyl radical having. at least 4 carbon atoms, x is the radical n is zero or a small whole number and M is a member of the group consisting of alkyl. metal or hydrogen radicals at least one M being a hydrogen or a metal radical.

2. Aymotor fuel comprising gasoline, tetraethyl lead in amounts sumcient to impart anti- I knock properties to said fuel, and about l-10% placed 12 inches from a mercury sunlamp of the of the weight of said tetraethyl lead of an oildispersible surface-active compoimd having the general formula in which R is an alkyl radical having at least 4 carbon atoms, X is the radical n is zero or a small whole number and M is a member of the group consisting of alkyl, metal or hydrogen radicals at least one M being a hydrogen or a metal radical.

3.' Gasoline containing 0.01% to about 0.25% of tetraethyl lead and about 0.0001% to 0.025% of an oil-dispersible surface-active compound having the general formula having the general formula in which R is an alkyl radical having at least 4 carbon atoms and M is a member of the group consisting of alkyl, metal or hydrogen radicals at least one M being a hydrogen or a metal radical.

5. Gasoline containing 0.01% to about 0.25% of tetraethyl lead and about 0.0001% to 0.025% of an oil-dispersible surface-active compound having the general formula 3 in which R is an alkyl radical having at least 4 carbon atoms.

6. Gasoline containing 0.01% to about 0.25% of tetraethyl lead and about 0.0001% to 0.025% of an oil-dispersible surface-active compound having the general formula in which R is an alkyl radical having at least 4 carbon atoms.

7. A method of stabilizing gasoline containing tetraethyl lead against tetraethyl lead deterioration and cloud formation which comprises adding to gasoline containing tetraethyl lead 0.0001% of an oil-'dispersible surface-active compound having the general formula in which R is an alkyl radical having at least 4 carbon atoms, X is the radical n is zero or a small whole number and M is a member of the group consisting of alkyl, metal or hydrogen radicals at least one M being a hydrogen or a metal radical.

8. A method of stabilizing gasoline containing tetraethyl lead against tetraethyl lead deterioration and cloud formation which comprises adding to gasoline containing tetraethyl lead 0.0001% to 0.025% or an oil-dispersible surface-active compound having the general formula in which R is an alkyl radical having at least 4 carbon atoms and M is a member of ,the group consisting of alkyl, metal or hydrogen radicals at least one M being a hydrogen or a metal radical.

Era/ran. w. COOK. WILLIAM B. THOMAS, JR. 

